You just wait for some time, you will get good results. Apart from it choose forum signature for backlinks.
Backlinks are the link which are placed on the other site which are coming to your site. As having the more backlinks for the website helsp to increase the ranking for the website.
Don't be upset for your PR. Just continue with building great back links. At the right time you will get your fruit. So enjoy!
When you're creating backlinks, remember to vary your anchor text. In natural backlinks, you can't have one anchor text for all incoming links. It look funny to Google.
Unlike Bing and Yahoo, Google's Organic Search Engine results is largely driven by backlink's (links from other sites pointing to yours).
please note that google not upgrade pr taking a/c of backlinks only and also its not time dependence.when your website is completely ok in eye of google ,then google will upgrade PR soon... just wait and watch....
Although Google haven't updated the PR that you seen on your PR Toolbar, the real PR of your page is a constantly changing thing and is regularly updated.
Assuming that all of the on-page optimization is done, all you can do is to wait. And build some more links while you wait.